Pimento cheese sandwiches for a tailgate: sharp cheddar spread on soft bread, cut into 24 tea sandwiches and kept on ice. No grill needed. About 40 min.
Brisket tacos for a crowd: smoke and chop brisket at home, then warm it and the tortillas on the grill at a Texas tailgate. Feeds 12, 40 min at the lot.
Hot chocolate for a crowd of 12, made from scratch at home, carried hot in a thermos, with a toppings bar at the lot. Kid-friendly. About 25 min of work.
Hot apple cider for a tailgate that serves 16: simmer it with spices at home, carry it hot in a thermos, add bourbon or rum by the cup. About 45 minutes.